1. Field of the Invention
The present invention relates to a medical image filing system and a medical image filing method that is incorporated in a PACS and stores (saves), transfers (distributes) and displays a medical image data. In particular, the present invention relates to a medical image filing system and a medical image filing method that preferably stores, transfers, and displays a large number of images collected with a modality (medical image tomography apparatus) of a multi-slice X-ray computerized tomography (CT).
2. Description of the Related Art
In general, a digital medical image data collected by a medical image tomography apparatus, such as an X-ray CT apparatus, are transferred to a PACS via a network. The PACS comprises a medical image filing system, and the transferred medical image data is received by the medical image filing system.
FIG. 8 is a block diagram showing the entire structure of a PACS using a conventional medical image filing system.
Referring to FIG. 8, a medical image filing system 101 comprises: a primary storage device 102; a reference-image storage device 103; a secondary storage device 104; and a server 105. The server 105 manages the output and input operation of a medical image data to/from the primary storage device 102, the reference-image storage device 103, and the secondary storage device 104. Therefore, specifically, the medical image data transferred from the medical image tomography apparatus 100 is processed by the server 105 as follows.                Store the medical image data in the primary storage device 102 (a fast drive, such as an hard disc drive (HDD)) (function which primarily stores image)        Store the medical image data stored in the primary storage device 102 to the secondary storage device 104 (media, such as a tape) (function which secondarily stores image)        Transfer the medical image data stored in the primary storage device 102 to a medical image display device 107 or an image-processing device (not shown) via the network (function which transmits image)        Display the medical image data stored in the primary storage device 102 on a first remote-terminal 106 (display a specific image with a Web technology: function which displays image).        Convert the medical image data stored in the primary storage device 102 into image data in a general image format and store the converted medical image data to the reference-image storage device 103 (function which stores reference-image)        Display the converted medical image data stored in the reference-image storage device 103 on a second remote-terminal 108 (display a simple image with the Web technology or refer to an in-hospital image: function which displays the reference-image)        
However, with the above-mentioned conventional medical image filing system, all pieces of the medical image data created in the medical image tomography apparatus are primarily stored, are secondarily stored, and are transferred and are displayed. Therefore, the following inconveniences are serious.
That is, with the appearance of the multi-slice X-ray CT apparatus, a large number of images with an excessively thinner-slice-thickness can be captured for a short time, as compared with the conventional X-ray CT apparatus. Thus, with the same tomography range as the conventional tomography range, a larger number of slice images are created.
Further, with the same slice thickness as the conventional slice thickness, one-time tomography operation ends for a shorter time, as compared with the conventional tomography operation, and the number of tomography times increases. As a consequence thereof, the number of slice images created per unit time sharply increases and, in proportional to the increase, the amount of created medical image data sharply increases. In future, the increase in speed of the multi-slice X-ray CT apparatus and the reduction in slice thickness will advance and it is predicted that the amount of medical image data will sharply and continuously increase.
The above-mentioned sharp increase in amount of medical image data causes the following obvious problems of the medical image filing system.                Shortage of capacity of the primary storage device (reduce a storing period on the on-line)        Increase costs due to the increase in media, serving as the secondary storage devices.        Delay the reference of image due to the extension of image transfer processing time and distributing processing time (display a specific image on the Web and display the image on the image display device)        Reduce a network throughput due to in-hospital distribution of a large number of images        Refer to unnecessary images on the reference of the simple image in the in-hospital distribution        
Usually, an examination image captured with the multi-slice X-ray CT includes a thick-slice image and a thin-slice image with the same tomography method or within the same tomography range (portion). The thick-slice image is referred to as a slice image, and the thin-slice image is used to obtain an image that can be easily interpreted in image processing including 3D processing and MPR processing. The image processing is performed immediately after the tomography operation (on the tomography day or in a few days after the tomography operation) and the image is additionally stored, as a processed image, in many cases. Rarely, the image that was captured is processed again. Further, upon referring to the simple image from sections in a hospital, the thin-slice image is not necessary.